What I mean't by simple FIS is that you were wondering about a possible personality disorder. FIS is often a co-morbid diagnosis with some personality disorders. It's possible to just have FIS/anxiety disorder without a personality disorder.

if it's just seeing how empty and blank I am. -- That is a common "complaint", if you will with FIS and other "issues". The person has numbed themselves to emotions, thus the empty feeling and feeling as though they are wearing a mask for the world.

Generally, FIS co-exists with anxiety and that is often the "prevailing" feeling a person experiences especially if they are faced with an emotionally intimate situation. It's the anxiety that causes them to recoil from the experience and pull away.

There are other possible explanations for your experience but I tend to lean toward the "simplest" explanation first. Not that FIS is an easy thing, it's just easier than a personality disorder which is often layered and combined with other things as well.

Bottomline, it's the pattern of negative self-thinking that often is the root of the issue you are describing. Usually, irrational and unfounded negative feelings about oneself. There are exercises for addressing that. Doing this kind of work really should be done with a therapist. There's more that goes into all this that you can't go to here. However, I will say that recognizing and accepting the things you've mentioned is certain a start.. Wanting to work on a problem is the beginning of recovery.

FoI symptoms have been present since I was old enough to go to school -- this implies some kind of emotional/physical trauma as a young child and may not be part of your consciousness. So, now, this could also include something else too.

I can venture this guess -- when your father passed away, your mother became overloaded, probably working a lot and distracted by various things and likely didn't connect with you on the level that a fully engaged parent would be able to do. She did the best she could, I"m sure, so we aren't blaming her. But, the lack of or lack of quality connection there would be a possible cause for all this. The lack of a connection to a male role model would also contribute.

If you can, see a therapist. It's worth the effort.